add pebble version check

bond.go

@@ -9,6 +9,7 @@ import (
 	"math"
 	"os"
 	"path/filepath"
+	"strconv"
 	"strings"
 
 	"github.com/cockroachdb/pebble"
@@ -141,6 +142,43 @@ func Open(dirname string, opts *Options) (DB, error) {
 		opts.PebbleOptions = DefaultPebbleOptions()
 	}
 
+	_, err := os.Stat(dirname)
+	if err != nil && !os.IsNotExist(err) {
+		return nil, err
+	}
+	if err != nil && os.IsNotExist(err) {
+		// create dir if db dir didn't exit.
+		if err := os.MkdirAll(dirname, os.ModePerm); err != nil {
+			return nil, err
+		}
+	}
+
+	// retive the pebble version.
+	version, err := os.ReadFile(filepath.Join(dirname, "VERSION"))
+	if err != nil && !os.IsNotExist(err) {
+		return nil, err
+	}
+
+	if err != nil && os.IsNotExist(err) {
+		// create version for to check invariant in the
+		// next open.
+		if err := os.WriteFile(filepath.Join(dirname, "VERSION"),
+			[]byte(fmt.Sprintf("%d", opts.PebbleOptions.FormatMajorVersion)),
+			os.ModePerm); err != nil {
+			return nil, err
+		}
+	} else {
+		existingVersion, err := strconv.ParseUint(string(version), 10, 64)
+		if err != nil {
+			return nil, err
+		}
+		if existingVersion != uint64(opts.PebbleOptions.FormatMajorVersion) {
+			return nil, fmt.Errorf("the user trying to open pebble version in %d. but db is in %d",
+				opts.PebbleOptions.FormatMajorVersion,
+				existingVersion)
+		}
+	}
+
 	opts.PebbleOptions.Comparer = DefaultKeyComparer()
 
 	pdb, err := pebble.Open(dirname, opts.PebbleOptions)

bond_test.go

@@ -1,9 +1,12 @@
 package bond
 
 import (
+	"fmt"
 	"os"
+	"path/filepath"
 	"testing"
 
+	"github.com/cockroachdb/pebble"
 	"github.com/stretchr/testify/require"
 )
 
@@ -42,3 +45,44 @@ func TestBond_Open(t *testing.T) {
 	err = db.Close()
 	require.NoError(t, err)
 }
+
+func TestBond_VersionCheck(t *testing.T) {
+	defer func() { _ = os.RemoveAll(dbName) }()
+
+	pebbleOpts := DefaultPebbleOptions()
+	pebbleOpts.FormatMajorVersion = pebble.FormatPrePebblev1MarkedCompacted
+	opts := DefaultOptions()
+	opts.PebbleOptions = pebbleOpts
+
+	db, err := Open(dbName, opts)
+	require.NoError(t, err)
+	err = db.Close()
+	require.NoError(t, err)
+
+	// simluate the db where VERSION file don't exist.
+	err = os.Remove(filepath.Join(dbName, "VERSION"))
+	require.NoError(t, err)
+
+	// opening db should create a version file
+	db, err = Open(dbName, opts)
+	require.NoError(t, err)
+	err = db.Close()
+	require.NoError(t, err)
+
+	_, err = os.Stat(filepath.Join(dbName, "VERSION"))
+	require.NoError(t, err)
+	buf, err := os.ReadFile(filepath.Join(dbName, "VERSION"))
+	require.NoError(t, err)
+	require.Equal(t, fmt.Sprintf("%d", opts.PebbleOptions.FormatMajorVersion), string(buf))
+
+	// rewrite the version with some other version.
+	err = os.Remove(filepath.Join(dbName, "VERSION"))
+	require.NoError(t, err)
+	err = os.WriteFile(filepath.Join(dbName, "VERSION"),
+		[]byte(fmt.Sprintf("%d", opts.PebbleOptions.FormatMajorVersion-1)), os.ModePerm)
+	require.NoError(t, err)
+
+	// throw an error since db is written in different version.
+	_, err = Open(dbName, opts)
+	require.Error(t, err)
+}